IN WATER CONTAINING FREE ACIDS. 189 



showing that the action of that acid on animal life is much 

 more marked than that of sulphuric. 



Sulphurous acid was next tried ; and the action of this 

 acid was very marked and rapid. 



For these observations I took some Rotifers and placed 

 them in pure water, free from acid. The sulphurous acid 

 was then added. 



On the addition of 0*002 grm. sulphurous acid per litre, 

 the appearance of the solution completely changed. The 

 Rotifers became more active, darting about, and making 

 such a great disturbance in the fluid that microscopical 

 examination became a matter of some difficulty. When 

 this acidity was raised to 0*004 grm. per litre, they became 

 quiet and very sluggish, a peculiar twitching action of the 

 tail being the only indication of life. 



The solution was now acidified to O'oi grm. per litre; 

 but by degrees all motion ceased, and about three hours 

 after the last addition of acid all life had become extinct. 

 The action of this acid is not so rapid as either that of 

 hydrochloric or sulphuric acid; a smaller amount, how- 

 ever, is required for the destruction of animal life. 



Water, acidified with 0*002 grm. sulphurous acid per 

 litre, was treated similarly to the former solutions, to see 

 if life could originate in water containing that amount of 

 free sulphurous acid; but after standing twenty-one days 

 no life was visible. I could not obtain any symptom of 

 life in water containing this acid. 



I do not consider these observations at all complete; 

 they only show the action of these acids on one species of 

 animal life, the Rotifers. If we took either a higher or a 

 lower degree of life, we should probably find that our 

 results would be in some degree different. 



